This invention relates to pressure cookers, and in particular to electric pressure cookers with an adiabatic cooking mode, capable of being remotely controlled.
The principle of cooking foods by steam pressure has been known since 1679 when Denis Papin, A French physicist, invented xe2x80x9cThe Papin Digesterxe2x80x9d a saucepan with an airtight lid which incorporated a safety valve, as reported in The New Encyclopaedia Britannica, 15th ed., Vol. 9. (1993), page 686. In 1939, the sauce pan-style pressure cooker was introduced by National Presto Industries and became a popular method of preparing food in one third the time while maintaining the vitamin and mineral content of foods and saving both food flavor and color. (Web site: http:  www.GoPresto.comxe2x80x94April, 2000.)
Many cooks embraced this European invention and used it to turn out meals from one-third to one-tenth the normal time. At the zenith of its popularity, at least one pressure cooker could be found in most well-equipped kitchens. However, with the advent of fast food restaurants, microwave cookery and some mispreceptions about the safety of the pressure cooker, this valuable utensil experienced a substantial decline in popularity.
In Europe, Japan and Korea, researchers have led the way to the development of today""s safe, silent, and sleek stainless-steel cookers, that are relied on for preparation of flavorful. nutritious meals. In Switzerland, for example, the average household owns three pressure cookers, according to Barry Bluestein and Kevin Morrissey, Express Cooking, HP Books, 2000, page 1. With the introduction of electric models that you simply program and walk away from, the pressure cooker may now experience a renaissance and move to the forefront of all time-saving devices used to prepare food. See CHEF""S; Professional Restaurant Equipment for the Home Chef Since 1979, page 57 of Late Spring 2000 catalog.
Focusing on various cookers that are plugged into electrical outlets for heating purposes, there are features that provide convenience and control to cooking appliances that have not heretofore been found in pressure cookers. For example, U.S. Pat. No. 3,908,111 describes a removable inner receptacle of metal or ceramic material that fits inside a primary vessel with a thermostatic electric heating element connected to the stationery metallic vessel with airspace between the two vessels. The primary vessel is used for high temperature cooking or frying and the inner receptacle is used for slow cooking or simmering. This gives versatility without a focus on saving energy or remote control operation. Likewise, U.S. Pat. No. 4, 591,698 discloses a dual, quick cooking utensil with an outer casing and a movable open inner pot for cooking and baking with a retractable power plug.
Other examples of versatile electric cookers are rice cookers which include U.S. Pat. No. 4,315,139 which discloses a rice cooker with a detachable cooking kettle separated from the heating kettle with a heat insulator having a timed thermo sensor. U. S. Pat. No. 4,421,974 claims an electric rice cooker with an improved timer that uses the xe2x80x9cafter heatxe2x80x9d to continue cooking when the heater is turned off, thus providing a means for conserving energy to effectively convert beta-starch to alpha-starch or xe2x80x9cripeningxe2x80x9d to produce tasty rice. U. S. Pat. No. 5,727,448 discloses an inner and outer kettle separated by an adiabatic vacuum member which prevents heat from escaping during the cooking process. The energy-conserving configuration is limited to an appliance for cooking rice.
Thermally insulated cooking utensils are disclosed in U.S. Pat. No. 5,031,519 which claims a cooking vessel with a heat-insulating lid; U. S. Pat. No. 5,567,458 has an insulated outer container wherein the insulation can be vacuum or thermal insulation and U.S. Pat. No. 5,643,485 discloses a cooking utensil with a closely spaced-apart controllable vacuum between an inner and outer chamber to activate or inactivate the insulating properties of the pot. Each cooking device has an inner container which is releasably housed in an outer chamber. Neither of these cooking devices has a pressure cooker as the inner chamber.
With regard to electric pressure cookers, U.S. Pat. No. 4,587,405 discloses an electrical heating element with a control circuit that allows preselection of cooking time. U.S. Pat. No. 5,839,357 uses a motor to safely lock both the food container and its lid and has a device for monitoring the inner pressure from the outside. Neither of the aforementioned electric pressure cookers have the novel sauce-pan style handle to safely lock the cooker. Even the traditional sauce-pan style pressure cookers have two handles that require two hands to rotate one handle clockwise and the other handle counterclockwise to seal the cooker. Electric pressure cookers are designed with two handles on the pot lids and two handles on the pot bottoms that are rotated, using two hands, in opposing directions to seal the vessel. Thus, a pressure cooker with a hinged handle that requires only one hand to operate the locking and unlocking means for the vessel would be easier to use, more efficient to operate and less expensive to manufacture. In addition, the present invention advances the art of pressure cooking by providing for remote operation and a means for conserving energy. With the ever-increasing costs of all types of fuel, it would be advantageous to insure that every appliance use the least amount of energy.
Thus, for the increasing numbers of busy, health-conscious consumers who want good nutritious food and don""t want to spend hours cooking it, there is a need for a pressure cooker that turns out healthy, low-fat meals safely, in record time with minimal supervision, while conserving energy and at fingertip command, if desired. The present invention provides novel improvements which make the safer, quieter, electric pressure cooker more efficient, more convenient to use and more energy saving.
One unexpected and unobvious result gained by the use of the present invention is the preparation of perfectly cooked foodstuffs while saving energy in a two-mode pressure cooking process. Cooking mode one is active heating or steaming and cooking mode two is allowing the retained heat to complete the cooking process while the pressure cooker returns to ambient conditions.
The first objective of the present invention is to provide an energy-saving, pressure cooking device that prepares healthy, nutritious foodstuffs, cooked under pressure, with minimal heat loss.
The second objective of this invention is to provide a pressure cooking device that has an adiabatic cooking mode, thus shortening the required heating time.
The third objective of the present invention is to provide a pressure cooking device that is flexible and the cooking time can be remotely controlled by telephone or computer.
The fourth objective of the present invention is to provide a pressure cooking device that can be operated with 120 volts or 240 volts electric power.
The fifth objective of the present invention is to provide a steam cooking device with spaced apart support means or microfeet on the food container bottom to prevent foods from sticking to the bottom.
The sixth objective of the present invention is to provide a pressure cooking device that has a controlled heating time such that foods cannot be over boiled, burned or scorched on the bottom of the pot.
The seventh objective of the present invention is to provide a pressure cooking device that has a single handle that is used for locking and unlocking the cooker.
The eighth objective of the present invention is to provide a pressure cooking device that revitalizes interest in and use of pressure cookers.
The ninth objective of the present invention is to provide a pressure cooking device that encourages a preference for home-cooked meals rather than fast foods.
The tenth objective of the present invention is to provide a pressure cooking device that encourages in-home food preparation.
The eleventh objective of the present invention is to provide a pressure cooking device that is easy to clean.
A preferred embodiment of the pressure cooking device of the present invention comprises having an inner pressure cooker pot permanently housed in an outer pot which is separated from the inner pot by a hermetically-sealed vacuum space or any rigid insulation that has a melting point higher than 600xc2x0 C. The lid for the inner and outer pot configuration has a hinged handle that seals and locks the cooking device and covers a vent controlled release valve therein. Additional features of the pressure cooking device include an automatic timer for starting and stopping the heating power, a high-pressure safety valve, a removable heat control element causing the appliance to be fully immersible for cleaning, a ridged bottom surface (microfeet) of the cooking pot to prevent sticking, and a two-position 120 volt or 240 volt switch.
Further objectives and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated in the accompanying drawings.